Use of citric acid derivatives as pesticidal adjuvants

ABSTRACT

The invention provides the use as a pesticidal adjuvant of at least one citric acid derivative and compositions containing the derivative, which has a log octanol-water coefficient (log P) of 2.6 to 11 and an equivalent hydrocarbon (EH) value of 29 to 47. The invention has been shown to enhance the efficacy of a range of pesticides.

This application has been filed under 35 USC 371 as the national stage of international application PCT/EB99/03430, filed Oct. 22, 1999.

FIELD OF THE INVENTION

This invention relates to the novel use of citric acid derivatives in association with pesticides and also pesticidal compositions containing citric acid derivatives. In particular, the invention relates to compositions having fungicidal, herbicidal, insecticidal and acaricidal activity.

BACKGROUND OF THE INVENTION

Pesticidal compounds are typically used in the form of compositions containing one or more co-formulants, for example surfactants. For example, WO96/22020 discloses the use in a pesticidal composition of at least one aliphatic mono-, di- or tri-ester, with no mention of citric acid derivatives. WO90/13222 discloses plant-protecting preparations comprising certain citric acid derivatives that are different from those of the present invention. EP 0 579 052 deals with plant-protecting compositions comprising a biocide and an accelerator, for example linear diacid and esters thereof. GB 2 002 635 and DE 27 38 878 disclose pyrethroid-containing insecticidal compositions comprising citric acid esters to reduce the volatility of the active ingredient. JP 52 141853 provides plastic films containing trialkyl acetylcitrate with good resistance to fungus growth. We have found a new group of compounds, not previously used in association with pesticidal compounds, that can be used with advantage in association with pesticidal compounds.

DESCRIPTION

In a first aspect, the invention provides the use as a pesticidal adjuvant of at least one citric acid derivative, which has a log octanol-water coefficient (log P) of 2.6 to 11 (preferably 2.7 to 11, particularly 4 to 10.7, especially 4 to 10.3) and an equivalent hydrocarbon (EH) value of 29 to 47 (preferably 32 to 44).

We have found that the use of citric acid derivatives according to the invention which have little or no pesticidal activity in their own right, surprisingly aid the penetration of the pesticidal compound into the plant or plant tissue, thereby enhancing the efficacy of the pesticide in the pesticidal composition. This enhanced efficacy enables lower application rates. Lower application rates coupled with low toxicity of citric acid derivatives, leads to a reduction in the environmental impact.

In the context of the invention, the term adjuvant is a compound which enhances. the bioactivity of a pesticide, having no bioactivity in its own right.

In accordance with its normal meaning, the term pesticide, pesticidal etc, includes plant growth regulators (PGRs).

Advantageously, we have found that citric acid derivatives used as part of the invention as well as improving penetration of the pesticidal compound into the plant, are also effective solvents or co-solvents for use in pesticidal compositions. Citric acid derivatives are particularly effective in conjunction with those pesticides that are conventionally formulated as emulsifiable concentrates or emulsions in water, i.e. low to intermediate lipophilic pesticides.

Further advantages of citric acid derivatives include their low flash point and negligible odour compared with many other currently used adjuvants.

The log P value (octanol/water partition coefficient) of a compound is a measure of the solubility of the compound in water. The higher the log P the less soluble is the compound. The log P is calculated from the structure of the compound using the “clog P Program” (Pomona CollegeMed Chem Release 3.54, January 1988, provided by Daylight Chemical Information Systems Inc., Claremont, Calif.). The values generated by this program correlate well in general with those determined experimentally by methods well-known to those skilled in the art. Such experimental methods are difficult to apply accurately to compounds within the scope of this invention, and we therefore use the calculated values.

The equivalent hydrocarbon (EH) value of a compound is a measure of the volatility of a compound. The EH value is arrived at by adding the total number of carbon atoms in the molecule, adding five for any hydroxy group, one for any ether group, eight for any carboxyl group, and then adding three for each ester group. It has been found that EH values determined in this way correlate well with actual volatilities.

Preferred citric acid derivatives are those having the general formula (I)

wherein,

R¹, R² and R³, which may be the same or different, are C₁ to C₂₀ alkyl, C₂ to C₂₀ alkenyl or C₂ to C₂₀ alkynyl, each of which may be substituted by —OR⁶, where R⁶ is hydrogen or alkyl; or hydrogen;

R⁴ is hydrogen or —C(═O)R⁵, where R⁵ is as defined for R¹; and

R¹, R², R³ and R⁴ are chosen such that the log P and EH value of the citric acid derivative is as defined hereinabove.

Any alkyl group may be straight or branched and is preferably of 1 to 10 carbon atoms, especially 1 to 7 and particularly 1 to 5 carbon atoms.

Any alkenyl or alkynyl group may be straight or branched and is preferably of 2 to 7 carbon atoms and may contain up to 3 double or triple bonds which may be conjugated, for example vinyl, allyl, butadienyl or propargyl.

Preferably, at least two R¹, R² and R³ groups are not hydrogen.

Preferably R¹, R² and R³, which may be the same or different, are C₁ to C₂₀ alkyl, especially C₃ to C₈ alkyl.

Particularly preferred compounds are tri-n-butyl citrate (log P=4.3, EH=32) and O-acetyl tri-n-butyl citrate (log P=4.8, EH=32).

The citric acid derivative of the invention may exist as a single compound, however more commonly it exists as a mixture of compounds. Often, citric acid derivatives are only commercially available as mixtures obtained by fractional distillation. In cases such as these, the log P and EH values are average values.

In a further aspect, the invention provides a pesticidal composition comprising at least one pesticidal compound and at least one citric acid derivative defined hereinabove.

In another aspect, the invention provides a method of combating pests at a locus infested or liable to be infested therewith which comprises applying to said locus an effective amount of a pesticidal composition which comprises a pesticidal compound and at least one citric acid derivative as hereinabove described.

Suitable active ingredients which can be combined with the citric acid derivatives are especially those disclosed in “The Pesticidal Manual”, 11th Edition, published by Crop Protection Publications, and may for example be a herbicide, fungicide, insecticide, acaricide or PGR.

A suitable fungicide is for example

(i) a conazole sterol Δ¹⁴-demethylase inhibitor,

(ii) a sterol Δ¹⁴-reductase/Δ^(8,7)-isomerase reduction inhibitor based on a 1-[3-(4-tert-butylphenyl)-2-methylpropyl] group which is attached via the N-atom to piperidine or 2,6-dimethylmorpholine

(iii) a dithiocarbamate fungicide

(iv) a phthalimide fungicide in which a chloroalkylthio group is attached via the N-atom to the optionally hydrogenated phthalimide group.

(v) an anilide fungicide

(vi) an mbc fungicide.

(vii) a carbamate fungicide

(viii) a copper compound fungicide

(ix) a tin compound fungicide

(x) a strobilurin type fungicide,

(xi) a 2-anilinopyrimidine fungicide

(xii) a compound which causes systemic activated resistance, or

(xiii) a fungicide selected from the group consisting of chlorothalonil, dimethomorph, fenamidone, fenpiclonil, fluazinam, hymexazol, nuarimol, pencycuron, pyrifenox, thicyofen, probenazole, pyroquilon, tricyclazole, quaternary ammonium compounds, fludioxonil, quinoxyfen, famoxadone, diclocymet, spiroxamine, flumetover, fenhexamid, furametpyr, diflumetorim, fencaramid, carpropamid, sulfur and 5-chloro-6-(2-chloro-6-fluorophenyl)-7-N-(4-methylpiperidin-1-yl)[1,2,4]triazolo[1,5-a]pyrimidine.

Conazoles are defined in ISO standard 257 as compounds based on imidazole or 1,2,4-triazole and containing a halogenated phenyl group. Examples include prochloraz (and its metal complexes—especially the zinc, manganese or copper complex), propiconazole, flusilazole, hexaconazole, tebuconazole, difenoconazole, bromuconazole, cyproconazole, diniconazole, fenbuconazole, imibenconazole, furconazole, tetraconazole, myclobutanil, penconazole, fluquinconazole, azaconazole, imazalil, triflumizole, epoxiconazole, triticonazole, metconazole and oxpoconazole.

Examples of type (ii) fungicides include fenpropimorph and fenpropidin.

Examples of type (iii) fungicides include mancozeb and thiram.

Examples of type (iv) fungicides include folpet, captafol and captan.

Examples of type (v) fungicides include

a) 3′,5′-dichloroanilide fungicides in which the anilino nitrogen comprises a ring carrying two oxo substituents, in positions adjacent the nitrogen, e.g. iprodione, vinclozolin or procymidone, or

b) acetanilide fungicides, e.g. metalaxyl or ofurace,

c) sulfanilide fungicides, e.g. dichlofluanid,

d) benzanilide fungicides, e.g. flutolanil, and

e) heteroarylanilide fungicides, e.g. thifluzamide.

Examples of type (vi) fungicides include carbendazim, benomyl and thiophanate-methyl.

Examples of type (vii) fungicides include diethofencarb and propamocarb.

Examples of type (viii) fungicides include Bordeaux mixture, oxine-copper, copper oxychloride and copper naphthenate.

Examples of type (ix) fungicides include tributyltin oxide and tributyltin naphthenate.

Strobilurin type fungicides (type (x) fungicides) are methyl esters or N-methylamides of arylacetic acid in which the acetic acid also carries a methoxymethylene or methoxyimino substituent. The aryl group is usually a 2-substituted phenyl group and/or can be separated from the acetic acid by a linking group such as oxygen. Examples of such compounds are kresoxim-methyl, azoxystrobin, metominostrobin, trifloxystrobin and picoxystrobin.

Examples of type (xi) fungicides include pyrimethanil, mepanipyrim and cyprodinil.

An example of a type (xii) fungicide is that having the code number CGA 2425704, which is sold under the trade name “Bion” and whose proposed common name is acibenzolar.

Examples of herbicides which can be used in conjunction with the citric acid derivatives include

a) Acetolactate synthase inhibitors, e.g.

(i) sulfonylureas, such as chlorsulfuron, sulfometuron, metsulfuron, bensulfuron, chlorimuron, tribenuron, thifensulfuron, thiameturon, ethametsulfuron, nicosulfuron, rimsulfuron, azimsulfuron, cinosulfuron, prosulfuron, flazasulfuron, pyrazasulfuron, triasulfuron, primisulfuron, oxasulfuron, imazasulfuron, cyclosulfamuron, amidosulfuron, ethoxysulfuron, iodosulfuron, halosulfuron, triflusulfuron, flurpyrsulfuron, sulfosulfuron, foramsulfuron, tritosulfuron, trifloxysulfuron and foramsulfuron,

(ii) 4,6-dimethoxypyrimidinyloxy benzoic acid analogues, such as, pyrithiobac, bispyribac, pyriminobac and pyribenzoxin;

(iii) aryisulfonanilides, such as cloransulam, diclosulam, flumetsulam, metosulam and florasulam, and

(iv) benzenesulfonamides, such as flucarbazone and procarbazone

b) choroacetanilides, such as alachlor, metolachlor, acetochlor and propachlor,

c) dinitroanilines, such as trifluralin, pendimethalin and ethalfluralin,

d) HBNs, such as bromoxynil and ioxynil,

e) benzoic acids, such as dicamba and propyzamide,

f) phosphorus acid esters, such as glyphosate, glufosinate and bilanofos,

g) quaternary ammonium compounds, such as paraquat, diqaut and difenzoquat,

h) aryloxyalkanoic acids, such as 2,4-D, 2,4 DB, dichloprop, MCPA, mecoprop, diclofop, clomeprop, fluazifop, haloxyfop, fenoxaprop, quizalofop, propaquizafop, clodinafop and cyhalofop,

i) anilides, such as propanil and mefenacet,

j) protoporphorinogen oxidase inhibitors, e.g.

(i) diphenyl ethers, such as bifenox, lactofen, acifluorfen, fluoroglycofen, fomesafen, oxyfluorfen, chlomethoxyfen and acloniphen, or

(ii) 4-chlorophenylazoless, such as, pentoxazone, cinidon-ethyl, flumiclorac, pyraflufen, azafenidin, fluthiacet-methy, sulfentrazone, carfentrazone, isopropazol, profluazol, and

(iii) flumoxazin,

k) ureas, such as chlortoluron, isoproturon, daimuron, iinuron, monolinuron and thidiazuron,

l) uracils, such as bromacil and lenacil,

m) triazines, such as atrazine, simazine, cyananzine, symetryn, terbutryn, trietazine and triaziflam,

n) carbamates, such as desmedipham, phenmedipham, triallate, molinate, dimepiperate, isopropilate, thiobencarb, esprocarm and asulam,

o) pyridines, such as trichlopyr, picloram, diflufenican, fluroxypyr, thiazopyr and clopyralid,

p) pyrazoles, such as pyrazolate, pyrazoxyfen and benzofenap,

q) imidazolidinones, such as imazamethabenz, imazaquin, imazapyr, imazethapyr, imazamox and AC 263222,

r) cyclohexanediones, such as alloxydim, sethoxydim, cycloxydim, tralkoxydim, clethodim and mesotrione,

s) oxa- and thia-diazoles, such as oxadiazon, oxadiardyl and flufenacet, and

t) triazinones, such as, metamitron and metribuzin,

u) miscellaneous compounds, such as isoxaflutole, cinmethylin, bentazon, ethofumesate, metamitron, metribuzin, fluorochloridinone and quinmerac.

Examples of insecticides and acaricides which can be used in conjunction with the citric acid derivates include

a) chlorinated hydrocarbons, such as endosulfan and lindane,

b) nitroimines and cyanoimines, such as imidacloprid, thiamethoxam, thiacloprid and acetamiprid,

c) pyrazoles, such as fipronil, vaniliprole, ethiprole, fenpyroximate, chlofenapyr, tebufenpyrad and tolfenpyrad,

d) tin compouinds, such as fenbutatin and azocyclotin,

e) benzoylureas, such as chlorfluazuron, diflubenzuron, flucycloxuron, teflubenzuron, flufenoxuron, fluazuron, hexaflumuron, lufenuron, triflumuron and novaluron,

f) other ureas, such as hexythiazox, triazamate, diafenthiuiron and sulcofuron,

g) fermentation products, such as ivermectin, abamectin, spinosad, and, emamectin,

h) benzoylhydrazines, such as tebufenozide, halofenozide and methoxyfenozide,

i) carbamates, such as indoxacarb, bendiocarb, carbofuran, carbosulfan, propoxur, methiocarb, aldicarb, methomyl, thiofanox, thiodicarb, pirimicarb and cartap,

j) pyrethroids, e.g.

(i) esters, such as permethrin, cypermethrin, deltamethrin, cyhalothrin, cyfluthrin, tralomethrin, flumethrin, acrinathrin, fenvalerate, flucythrinate, fluvalinate, ZXI 8901, fenfluthrin, tefluthrin, biphenthrin, transfluthrin, tetramethrin, (including various stereo and/or geometric isomers of these compounds), and

(ii) non-esters, such as etofenprox, silafluofen, flufenprox, halfenprox and protrifenbute

k) miscellaneous compounds, such as benzoximate, pyridaben, fenoxycarb, pyriproxyfen, hydamethylnon, buprofezin, chinomethionat, clofentezine, acequinocyl, chlofenapyrfenazaquin, pyrimidifen and cyromazine.

Examples of PGRs are chlormequat, paclobutrazol and ethephon.

The names quoted for these compounds are the non-proprietary common names and the chemical structure can be found for example by reference to “The Pesticide Manual” ibid. Structures of compounds not in the Pesticide Manual can be found from the Compendium of Pesticide Common Names (http://www.hclrss.demon.co.uk/).

We have found that the invention is particularly useful with pesticides of high melting point, i.e. greater than 100° C. (especially greater than 130° C.), and/or low: solubility in organic solvents.

The citric acid derivatives of the invention are particularly efficacious with the following fungicides and groups of fungicides:

Conazoles (especially fluquinconazole or triticonazole), strobilurins (especially alkoxyacrylates e.g. azoxystrobin, or those containing an oximeamide moiety) or dimethomorph.

The citric acid derivatives of the invention are particularly efficacious with the following herbicides and groups of herbicides:

Alkyldiaminotriazines (especially triaziflam), aryloxyalkanoic acids and esters (especially fenoxaprop, quizalofop, fluazifop), pyridines (especially fluoroxypyr), carbamates (especially phenmedipham or desmedipham), protoporphorinogen oxidase inhibitors (especially carfentrazone), sulfonylureas (especially nicosulfuron), HBNs, cyclohexanediones (especially mesotrione), imidazolidinones (especially imazapyr) and isoxaflutol.

The citric acid derivatives of the invention are particularly efficacious with the following insecticides:

Fipronil, indoxacarb, endosulfan, pirimicarb or clofentezine.

The citric acid derivative is preferably applied at a rate of 20 g to 2000 g, especially 50 g to 500 g, per 100 liters of the diluted formulation.

The citric acid derivative may be incorporated in conventional formulations (e.g. emulsions in water, suspoemulsions or solid formulation types after adsorption onto a suitable inert carrier, such as water dispersible granules) or may be added (“tank-mixed”) to the pesticide just prior to use. It may be desirable also to add small quantities of solvent and/or surfactant, especially a non-ionic surfactant, and other additives such as fatty acids to improve the emulsifiability of the citric acid derivative. Typically, the amount of emulsifier is 1 to 20% of the citric acid derivative. The choice of emulsifier is not critical to the performance of the invention, however alcohol ethoxylate surfactants form a preferred group.

The weight ratio of the pesticidal compound to citric acid derivative is preferably 1 to 50, especially 1 to 10.

EXAMPLE

The following Examples show how the pesticidal adjuvants of the invention enhance the efficacy of a variety of pesticidal active ingredients.

Examples 1 and 2 show enhancement of fungicidal efficacy against Erysiphe graminis (powdery mildew) and Plasmopara viticola respectively.

Example 3 shows enhancement of herbicidal efficacy against a number of common weeds.

Example 4 shows enhancement of insecticidal efficacy against Aphis fabae.

Example 5 shows enhancement of insecticidal efficacy against the eggs of Tetranychus urticae (red spider mite).

Example 1—Fungicidal Efficacy

In a glasshouse, wheat plants were inoculated with Erysiphe graminis (powdery mildew). One day after inoculation, the plants were sprayed with various fungicidal mixtures.

The spray mixtures were prepared by diluting with water a commercial composition of the active ingredient and optionally a solution of the citric acid derivative and emulsifier. When present, the citric acid derivative was either tributyl citrate (TBC) or O-acetyl tributyl citrate (ATBC), and constituted 0.25% w/v of the mixture (see Table A). The solution of citric acid derivative contained 20% emulsifier. The emulsifier was commercially available Synperonic A5 (supplied by Uniqema)

The concentration of active ingredient was selected to give an application rate shown in Table A.

The commercial compositions of the active ingredients used in preparing the spray mixtures are given below.

Fluquinconazole—Commercial composition sold as Castellan

Azoxystrobin—Commercial composition sold as Amistar

Triticonazole—Non-commercial composition formulated in-house to give a 10SC from technical grade triticonazole

One week after spraying, the wheat was assessed for control of disease. The results are shown in Table A. The degree of control, shown in the right hand side column, is the average of seven replicates.

TABLE A Active ingredient Mix (Rate g/ha) Adjuvant % Control 1a Fluquinconazole (250) nil 19.6 2a Fluquinconazole (250) TBC 97.1 3a Fluquinconazole (250) ATBC 96.1 4a Azoxystrobin (250) nil 19.6 5a Azoxystrobin (250) TBC 90.2 6a Azoxystrobin (250) ATBC 85.3 7a Triticonazole (250) nil 30.2 8a Triticonazole (250) TBC 65.1 9a Triticonazole (250) ATBC 73 10a Triticonazole (125) nil 24.8 11a Triticonazole (125) TBC 77.8 12a Triticonazole (125) ATBC 77.8 13a Triticonazole (62.5) nil 11.1 14a Triticonazole (62.5) TBC 63.5 15a Triticonazole (62.5) ATBC 65.1

Example 2—Fungicidal Efficacy

Using the same method as Example 1 vine seedlings were inoculated with Plasmopara viticola and sprayed with various mixtures shown in Table B. The spray mixtures were prepared in analogous fashion to Example 1 using dimethomorph as the active ingredient. The commercial composition of dimethomorph used was Forum.

The mixtures were sprayed on to the plants at a rate of 2.5 g of active ingredient per 100 liters of spray mixture.

One week after spraying, the wheat was assessed for control of disease. The results are shown in Table B. The degree of control, shown in the right hand side column, is the average of five replicates.

TABLE B Mix Active ingredient Adjuvant % Control 1b Dimethomorph nil 65.3 2b Dimethomorph TBC 96.4 3b Dimethomorph ATBC 72.02

Example 3—Herbicidal Efficacy

Seeds of the test species shown in Table C were sown in sandy loam soil and were grown in the glasshouse to the growth stages shown in Table C. Each species was then sprayed with various spray mixtures.

TABLE C BROAD-LEAVED GRASSES Scientific Growth Scientific Growth name Code Stage name Code Stage Amaranthus AMARE 11 Lokum LOLMU 12 retroflexus multiflorum Chenopodium CHEAL 11 Alopecurus ALOMY 12 album myosuriodes Stellaria STEME 11-12 Echinochloa ECHCG 12 media crus-galli Gallum GALAP 10-11 Setaria SETVI 11 aparine viridis Pharbitis PHBPU 11-12 Digitaria DIGSA 11-12 purpurea adscendens

The spray mixtures were prepared in analogous fashion to Example 1. The active ingredient and citric acid derivative, and the concentration thereof, was selected to give an application rate shown in Table D.

The commercial compositions of the active ingredients used in preparing the spray mixtures are given below.

Carfentrazone—Commercial composition (WG50) sold as Affinity

Triaziflam—Commercial composition (EW30)

Imazethapyr—Commercial composition (EC24) sold as Pursuit.

Nicosulfuron—Commercial composition (SC04) sold as Milagro.

Mesotrione—Non-commercial composition (WP20) made in-house.

Mixtures were sprayed at a rate of 300 liter of spray mixture/hectare. In all cases two replicates were done. After spraying, the sprayed mixture was allowed to dry and the pots were returned to the glasshouse.

The herbicidal effects were assessed visually over a period of 3 weeks. Visual assessment were on a 100% basis (0=no effect compared to untreated plants; 100=complete kill of test species). The results are shown in Table D. Tributyl citrate and O-acetyl tributyl citrate in the absence of any active ingredient caused no herbicidal effects (see experiments 26d to 29d).

TABLE D Active Ingredient Adjuvant Mix (rate kg/ha) (rate kg/ha) LOLMU ALOMY ECHCG SETVI DIGSA AMARE CHEAL STEME GALAP PHBPU MEAN  1d Carfentrazone nil 0 0 0 5 0 80 85 30 70 100 37 (0.02)  2d Carfentrazone ATBC (0.3) 0 0 40 50 0 95 100 10 75 100 47 (0.02)  3d Carfentrazone ATBC (0.9) 0 0 30 45 0 90 90 10 100 100 47 (0.02)  4d Carfentrazone TBC (0.3) 0 0 40 55 10 80 95 0 98 100 48 (0.02)  5d Carfentrazone TBC (0.9) 0 0 10 50 0 95 90 10 100 100 46 (0.02)  6d Triaziflam nil 0 10 10 10 0 70 70 10 70 95 31 (0.08)  7d Triaziflam ATBC (0.3) 40 40 40 20 10 90 95 10 75 70 49 (0.08)  8d Triaziflam ATBC (0.9) 0 30 50 50 0 95 95 20 80 90 51 (0.08)  9d Triaziflam TBC (0.3) 50 30 50 10 10 80 90 10 60 95 49 (0.08) 10d Triaziflam TBC (0.9) 10 10 90 20 30 85 95 20 60 98 52 (0.08) 11d Imazethapyr nil 0 0 10 40 0 80 30 75 40 15 29 (0.02) 12d Imazethapyr ATBC (0.3) 10 0 80 55 55 75 55 75 40 20 47 (0.02) 13d Imazethapyr ATBC (0.9) 30 20 80 55 50 75 40 70 85 15 52 (0.02) 14d Imazethapyr TBC (0.3) 0 10 80 60 55 70 60 80 70 20 51 (0.02) 15d Imazethapyr TBC (0.9) 10 0 80 65 50 85 60 80 65 20 52 (0.02) 16d Nicosulfuron nil 0 10 0 10 0 50 5 5 25 0 11 (0.02) 17d Nicosulfuron ATBC (0.3) 0 10 20 40 0 60 10 0 25 10 18 (0.02) 18d Nicosulfuron ATBC (0.9) 10 30 40 70 10 60 10 0 40 10 28 (0.02) 19d Nicosulfuron TBC (0.3) 0 10 30 50 0 40 10 0 20 0 16 (0.02) 20d Nicosulfuron TBC (0.9) 0 10 45 50 15 55 10 0 0 15 20 (0.02) 21d Mesotrione nil 0 0 40 0 30 80 85 85 65 65 45 (0.08) 22d Mesotrione ATBC (0.3) 0 5 80 0 75 70 90 70 65 65 52 (0.08) 23d Mesotrione ATBC (0.9) 0 25 85 20 80 70 95 73 68 75 59 (0.08) 24d Mesotrione TBC (0.3) 0 10 85 10 85 70 90 75 63 65 55 (0.08) 25d Mesotrione TBC (0.9) 0 40 85 20 83 73 90 58 80 70 60 (0.08) 26d   — ATBC (0.3) 0 0 0 0 0 0 0 0 0 0 0 27d   — ATBC (0.9) 0 0 0 0 0 0 0 0 0 0 0 28d   — TBC (0.3) 0 0 0 0 0 0 0 0 0 0 0 29d   — TBC (0.9) 0 0 0 0 0 0 0 0 0 0 0

Example 4—Insecticidal Efficacy

Three-week old bean plants (Vicia faba) were sprayed three times to runoff with various mixtures.

The spray mixtures were prepared in analogous fashion to Example 1. The active ingredient and citric acid derivative, and the concentration thereof, was selected to give an application rate shown in Table E. The citric acid derivative was tributyl citrate (TBC).

The commercial compositions of the active ingredients used in preparing the spray mixtures are given below.

Endosulfan—Commercial composition (EC35) sold as Thiodan.

Deltamethrin—Commercial composition (EC2.5) sold as Decis.

Pirimicarb—Commercial composition (SG 50) sold as Pirimor.

Fipronil—Commercial composition (WG80) sold as Regent.

The plants were infested with Aphis fabae and the degree of mortality was measured 3 days and 7 days after infestation. The results are shown in columns 4 and 5 of Table E.

In order to test persistency, some of the plants were re-infested 3 days after the first infestation and the degree of mortality was measured 3 and 7 days after re-infestation. The results are shown in columns 6 and 7 of Table E. To test the persistency further, some of the plants were re-infested 7 days after the first infestation and the degree of mortality was measured 3 and 7 days after the second re-infestation. The results are shown in columns 8 and 9 of Table E.

The experiments were conducted at 25° C. and 60% humidity. Each result was the average of two replications.

TABLE E Infested @ Reinfested@ Reinfested @ 0 days 3 days 7 days Active ingredient 3 7 3 7 3 7 Mix (rate g/ha) Adj. days days days days days days  1e Endosulfan (10) nil 75 40 15 10 0 0  2e Endosulfan (10) TBC 98 96 80 63 23 10  3e Endosulfan (3) nil 23 8 0 0 0 0  4e Endosulfan (3) TBC 88 83 15 0 0 0  5e Endosulfan (1) nil 0 0 0 0 0 0  6e Endosulfan (1) TBC 20 15 0 0 0 0  7e Deltamethrin (0.03) nil 99 99 98 97 90 80  8e Deltamethrin (0.03) TBC 100 98 93 92 90 85  9e Deltamethrin (0.01) nil 96 93 80 68 65 30 10e Deltamethrin (0.01) TBC 97 94 93 88 65 45 11e Deltamethrin (0.003) nil 80 75 15 8 10 0 12e Deltamethrin (0.003) TBC 78 68 75 58 20 10 13e Pirimicarb (0.3) nil 20 20 0 0 0 0 14e Pirimicarb (0.3) TBC 83 65 30 15 15 0 15e Pirimicarb (0.1) nil 0 0 0 0 0 0 16e Pirimicarb (0.1) TBC 25 10 18 0 0 0 17e Fipronil (0.3) nil 88 85 35 30 0 0 18e Fipronil (0.3) TBC 98 98 95 93 85 80 19e Fipronil (0.1) nil 65 55 15 10 0 0 20e Fipronil (0.1) TBC 63 63 65 65 45 40

Example 5—Insecticidal (Ovicide) Efficacy

Four week old bean plants were infested with a mixed population of the eggs of Tetranychus urticae (red spider mites). After 24 and 48 hours the motile stages were removed with pressurised air. The plants were sprayed to runoff with various spray mixtures.

The spray mixtures were prepared in analogous fashion to Example 1 using clofentezine at rates given in Table F. The citric acid derivative was tributyl citrate (TBC).

The compositions were prepared from commercially available Clofentezine SC 42 (Apollo). The plants were placed in the glass house at 23° C. and 60% humidity.

The mortality of the eggs was assessed after 10 and 14 days. The results are shown in Table F.

TABLE F Active ingredient Mix (Rate g/ha) Ajuvant 10 days 14 days 1f Clofentezine (10) nil 99 97 2f Clofentezine (10) TBC 100 100 3f Clofentezine (3) nil 98 95 4f Clofentezine (3) TBC 100 100 5f Clofentezine (1) nil 70 50 6f Clofentezine (1) TBC 100 100 7f Clofentezine (0.3) nil 40 25 8f Clofentezine (0.3) TBC 70 93 

What is claimed is:
 1. A method of enhancing the penetration of a pesticide into a plant or plant tissue comprising applying said pesticide in combination with an adjuvant to said plant or plant tissue infested or liable to be infested by a pest, wherein said adjuvant is a citric acid derivative of the formula (I)

wherein, R¹, R² and R³, which may be the same or different, are C₁ to C₂₀ alkyl, C₂ to C₂₀ alkenyl or C₂ to C₂₀ alkynyl, each of which may be substituted by —OR⁶, where R⁶ is hydrogen or alkyl; or hydrogen; R⁴ is hydrogen or —C(═O)R⁵, where R⁵ is as defined for R¹; and wherein R¹, R², R³ and R⁴ are chosen such that said derivative has a log octanol-water coefficient (log P) of 2.6 to 11 and an equivalent hydrocarbon (EH) value of 29 to
 47. 2. The method according to claim 1 where the log P is 2.7 to
 11. 3. The method according to claim 2 where the EH is 32 to
 34. 4. The method according to claim 3 where the log P is 4 to 10.7.
 5. The method according to claim 3 where the log P is 4 to 10.3.
 6. The method according to claim 1 where the EH is 32 to
 34. 7. The method according to claim 1 where the log P is 4 to 10.7.
 8. The method according to claim 1 where the log P is 4 to 10.3.
 9. The method according to claim 1 where the pesticide has a melting point greater than 100° C.
 10. The method according to claim 9 where the pesticide has a melting point greater than 130° C. 